A graphene has attracted great expectations from materials such as next generation displays, electronic devices, and photoelectric devices due to excellent properties such as physical and chemical stabilities, electric conductivity, charge mobility, flexibility, transparency, etc.
However, unlike semiconductor materials in which electrical conductivity is easily controlled through a finite band gap at a Fermi level, the graphene has a limit in that it is difficult to control the electric conductivity because the graphene does not have the band gap.
In order to overcome the limitations in unique physical properties of the graphene, a research has been continuously studied to induce formation of the band gap on a graphene electron band structure. However, since the graphene has a partial lattice symmetry that protects a Dirac point on a Dirac electron band structure, which is present in a single atomic layer, it is very difficult to manipulate the graphene.
Accordingly, different two-dimensional semiconductor materials having a band gap in a natural state unlike the graphene have been intensively focused.
The two-dimensional semiconductor materials, which are the first to be spotlighted, are transition metal chalcogen compounds such as MoS2, MoSe2, MoTe2, WS2 or WSe2, etc., and have band gaps in the range of about 1.4 to 2.0 eV, which makes it much easier to control electric conductivity as compared to the graphene. However, these two-dimensional semiconductor materials have limitations in that charge mobility is much lower than that of the graphene, and is similar to those of silicon and germanium (Japanese Patent Laid-Open Publication No. 2015-090984).
Accordingly, black phosphorus has newly emerged as a two-dimensional semiconductor material in recent years. The black phosphorus is a material composed of phosphorus (P) atoms, which has an atomic arrangement of puckered honeycomb structures similar to graphene. However, the black phosphorus has advantages in that the electric conductivity is easily controlled and the charge mobility is excellent by having an appropriate size of band gap value between graphene having a band gap value of 0 eV and a transition metal chalcogen compound having a band gap value between 1.4 and 2.0 eV.
When a transistor is manufactured by using the black phosphorus as a material, there is a limitation in that the charge mobility is decreased since black phosphorus which is a p-type semiconductor and a different material which is a n-type semiconductor form a hetero-junction in a vertical direction to manufacture the transistor.
Therefore, the present inventors found that when a homo-junction black phosphorus thin film is manufactured by converting some regions of the black phosphorus into a n-type semiconductor in order to prevent the decrease in charge mobility, the decrease in charge mobility due to charge transfer between different materials could be prevented, and completed the present invention.